Conventional electromagnetic coupling devices, particularly electromagnetic clutches mounted on vehicle air conditioner compressors have a magnetizing coil with multiple wound turns. The magnetizing coil is covered with an insulating resin and fit into an annular groove in a yoke. The starting end of the wound section and the final end of the wound section of the magnetizing coil are drawn outside through through-holes in a pair of rubber bushings press-fit into passages through the bottom of the yoke. Each end of the magnetizing coil, which is drawn out, is connected to a pair of terminals in a terminal block that is affixed to the back of the yoke. A diode is connected to the terminals and is in parallel to the magnetizing coil as shown in Japanese Kokoku Patent No. Hei 6[1994]-48020. The terminals are formed from thin sheet metal material by stamping and bending. A pair of slits are formed in a first connection section of each terminal for receiving a lead from the magnetic coil. A second connection section of each terminal has slits for receiving a lead from the diode. A third connecting section of each terminal is connectable to a power source. The two terminals are placed in an injection molding machine and partially encased in a resin terminal block. The terminal block is then secured to the yoke.
After the terminal block is affixed to and held by the yoke, each end of the magnetizing coil is drawn outside through a through-hole in a rubber bushing from the annular groove in the yoke. The coil leads are each connected to the first connection section of one of the terminal in the terminal block. The diode leads are connected to the second connection section of each terminal. A cover made of resin material is pressed and fitted to the edge of the opening of the terminal block, with an elastic packing material held between them, and the inside of the terminal block is insulated by being closed off from the outside.
U.S. Pat. No. 4,935,713 issued to Bekheet discloses an electromagnet in an electromagnetic clutch having a yoke in which an annular groove is formed. A coil bobbin is integrally formed with a square columnar terminal holder section as a terminal block that passes externally through a nearly rectangular through-hole through the bottom of the aforementioned yoke. A magnetizing coil is positioned inside the coil bobbin inside the yoke. A coil cover that covers the end of the magnetizing coil, which is exposed beyond the coil bobbin's surrounding section is pressed into the yoke's annular groove and is secured in place. A terminal housing fits into the terminal holder section of the coil bobbin in which a pair of terminals are mounted.
The electromagnet of a conventional electromagnetic coupling device has the starting end of the wound section and the final end of the wound section of a magnetizing coil, which is previously wound in multiple turns, inserted into a pair of insertion holes through the terminal holder section of the coil bobbin, while at the same time nearly half of the magnetizing coil fits into an annular groove in the coil bobbin. The approximately half of the magnetizing coil that is exposed beyond the annular groove of the coil bobbin is covered by a coil cover. The coil assembly made up of this coil bobbin, magnetizing coil, and coil cover is pressed into the yoke's annular groove while the terminal support section of the coil bobbin is drawn outside through a through-hole in the yoke. After the coil assembly is pressed in, part of the edge of the opening in the yoke plastically flows toward the annular groove and the coil assembly is secured inside the yoke's annular groove. A first connection section for each terminal, in which a slit is formed, is pressed into each open section of the terminal support section. A lead from the magnetizing coil is forced into the slit in the first connection section as each terminal is pressed into an open section. A terminal housing is slid down over the two terminals and the terminal support section of the coil bobbin. A pair of cut pieces on an attaching plate fused to the back of the yoke are bent, by press working, into depression sections formed in a pair of flanges on the terminal housing so that the coil bobbin terminal holder section is secured to and held by the yoke while covered by the terminal housing. Thus, the electromagnet of this electromagnetic coupling device can be connected to the terminal's first connection section without externally exposing the starting end of the wound section and the final end of the wound section of the magnetizing coil, which is pressed into the yoke's annular groove.
The electromagnet in the conventional electromagnetic coupling device disclosed in Japanese Kokoku Patent No. Hei 6[1994]-48020 uses a structure in which a pair of terminals is injection-molded in a terminal block made of resin material in advance so that the terminals will be separated and parallel. The starting end of the wound section, the final end of the wound section of the magnetizing coil, and each of the diode lead wires will be connected to the first and second connection sections of the terminals. A process in which each end section of the magnetizing coil is connected to a terminal's first connection section, a process in which each lead wire of the diode is connected to a terminal's second connection section, and further, a process in which a cover is press-fit into the terminal block, with an elastic material packing between them, and secured is required. These assembly processes are tedious, time consuming and difficult. They are completed manually. The leads from the magnetizing coil and from the diodes are relatively long and unsupported. As a result of their unsupported length the leads may break when exposed to vibration. Magnetic clutches for air conditioner compressors are subjected to the vibrations from the engine to which the compressor is attached. Over time the vibrations can cause lead breakage and clutch failures.